U.S. patent application number 10/686874 was filed with the patent office on 2005-04-21 for energy storage flywheel auxiliary bearing system and method.
Invention is credited to Brault, Sharon K., Giles, Todd R., Potter, Calvin C., Wingett, Paul T..
Application Number | 20050082928 10/686874 |
Document ID | / |
Family ID | 34520816 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050082928 |
Kind Code |
A1 |
Giles, Todd R. ; et
al. |
April 21, 2005 |
Energy storage flywheel auxiliary bearing system and method
Abstract
An energy storage flywheel system includes a shaft, one or more
primary bearing assemblies, and one or more secondary bearing
assemblies. A secondary bearing control circuit determines the
operability of the primary bearing assemblies and, based on this
determination, selectively engages the secondary bearing assemblies
to rotationally support the flywheel shaft.
Inventors: |
Giles, Todd R.; (Phoenix,
AZ) ; Wingett, Paul T.; (Mesa, AZ) ; Potter,
Calvin C.; (Mesa, AZ) ; Brault, Sharon K.;
(Chandler, AZ) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Family ID: |
34520816 |
Appl. No.: |
10/686874 |
Filed: |
October 15, 2003 |
Current U.S.
Class: |
310/90.5 |
Current CPC
Class: |
H02J 1/16 20130101; Y02E
60/16 20130101; H02K 7/025 20130101 |
Class at
Publication: |
310/090.5 |
International
Class: |
H02K 007/09 |
Claims
We claim:
1. An energy storage flywheel system, comprising: a shaft; a
flywheel assembly mounted on the shaft; one or more primary bearing
assemblies each configured to selectively rotationally support the
shaft; one or more secondary bearing assemblies each configured to
selectively rotationally support the shaft; one or more secondary
bearing position sensors each configured to supply position signals
representative of a position of one or more of the secondary
bearing assemblies; a secondary bearing control circuit adapted to
receive (i) one or more signals representative of primary bearing
assembly operability and (ii) the secondary bearing assembly
position signals and operable, in response thereto, to selectively
supply actuator control signals; and one or more secondary bearing
actuator assemblies each coupled to one or more of the secondary
bearing assemblies, each actuator assembly further coupled to
receive the actuator control signals from the control circuit and
operable, in response thereto, to move the secondary bearing
assemblies to one of (i) an engage position, in which each
secondary bearing assembly rotationally supports the shaft, and
(ii) a disengage position, in which each secondary bearing assembly
does not rotationally supports the shaft.
2. The system of claim 1, wherein each secondary bearing actuator
comprises: a motor coupled to receive the actuator control signals
and operable, in response thereto, to supply a drive force; and an
actuator coupled to receive the drive force and operable, in
response thereto, to selectively move one or more of the secondary
bearing assemblies between the engage and disengage positions.
3. The system of claim 1, wherein the control circuit is further
operable to selectively supply one or more brake control signals,
and wherein each the system further comprises: a brake assembly
coupled to the secondary bearing actuator, the brake assembly
further coupled to receive the brake control signals and operable,
in response thereto, to selectively inhibit movement of one or more
of the secondary bearing actuator assemblies.
4. The system of claim 3, wherein the brake assembly comprises: a
first plate coupled to the secondary bearing actuator assembly, the
first plate having at least a first surface and a second surface,
the first surface having a plurality of teeth formed thereon; a
second plate having at least a first surface and a second surface,
the second plate second surface located substantially opposed to
the first plate first surface and having a plurality of teeth
formed thereon; and a brake actuator coupled to the second plate,
the brake actuator coupled to receive the brake control signals and
operable, in response thereto, to selectively move the second plate
second surface into and out of engagement with the first plate
first surface.
5. The system of claim 1, wherein each primary bearing assembly
comprises a magnetic bearing assembly, each magnetic bearing
assembly adapted to be selectively activated and deactivated, and
configured, when activated, to rotationally mount the flywheel
assembly in non-contact manner, and wherein the system further
comprises: a magnetic bearing control circuit configured to supply
magnetic bearing activation control signals to each magnetic
bearing assembly and adapted to receive one or more magnetic
bearing monitor signals, the magnetic bearing control circuit
further configured, in response to the magnetic bearing monitor
signals, to supply the signals representative of primary bearing
assembly operability to the secondary bearing control circuit.
6. The system of claim 1, wherein each of the secondary bearing
assemblies comprises a mechanical bearing assembly.
7. The system of claim 1, wherein the secondary bearing control
circuit is further adapted to receive a signal representative of an
electrical system supply voltage and is further operable, in
response thereto, to selectively supply the actuator control
signals.
8. The system of claim 1, wherein each secondary bearing position
sensor comprises a proximity sensor.
9. The system of claim 1, wherein the secondary bearing position
sensors comprise: an engage position sensor configured to supply an
engage signal when the secondary bearing assemblies are at least in
the engaged position; and a disengage position sensor configured to
supply a disengage signal when the secondary bearing assemblies are
at least in the disengaged position.
10. The system of claim 9, further comprising: a sensor mount
structure disposed proximate at least one secondary bearing
actuator assembly, the sensor mount structure having a main body
that includes at least a first end and a second end, the sensor
mount structure first end having the engage position sensor mounted
therein and the sensor mount structure second end having the
disengage position sensor mounted therein; a position semaphore
having at least a first end and a second end, the position
semaphore first end coupled to the at least one secondary bearing
actuator assembly and moveable therewith and the position semaphore
second end disposed between the sensor mount structure first and
second ends, wherein the engage and disengage position sensors are
each proximity sensors operable to supply position signals based on
proximity thereto of the position semaphore.
11. The system of claim 1, further comprising: one or more bearing
mount structures each coupled to one of the secondary bearing
assembly actuator assemblies, each bearing mount structure having
one or more of the secondary bearing assemblies mounted thereon,
wherein the secondary bearing actuator assemblies selectively move
the bearing mount structures to thereby move the secondary bearing
assemblies.
12. An auxiliary bearing control system for a shaft that is
selectively rotationally supported by one or more primary bearing
assemblies, comprising: one or more secondary bearing assemblies
each configured to selectively rotationally support the shaft; one
or more secondary bearing position sensors each configured to
supply position signals representative of a position of one or more
of the secondary bearing assemblies; a secondary bearing control
circuit adapted to receive (i) one or more signals representative
of primary bearing assembly operability and (ii) the secondary
bearing assembly position signals and operable, in response
thereto, to selectively supply actuator control signals; and one or
more secondary bearing actuator assemblies each coupled to one or
more of the secondary bearing assemblies, each actuator assembly
further coupled to receive the actuator control signals from the
control circuit and operable, in response thereto, to move the
secondary bearing assemblies to one of (i) an engage position, in
which each secondary bearing assembly rotationally supports the
shaft, and (ii) a disengage position, in which each secondary
bearing assembly does not rotationally supports the shaft.
13. The system of claim 12, wherein each secondary bearing actuator
comprises: a motor coupled to receive the actuator control signals
and operable, in response thereto, to supply a drive force; and an
actuator coupled to receive the drive force and operable, in
response thereto, to selectively move one or more of the secondary
bearing assemblies between the engage and disengage positions.
14. The system of claim 12, wherein the control circuit is further
operable to selectively supply one or more brake control signals,
and wherein the system further comprises: a brake assembly coupled
to one or more of the secondary bearing actuator assemblies, the
brake assembly further coupled to receive the brake control signals
and operable, in response thereto, to selectively inhibit movement
of one or more of the secondary bearing actuator assemblies.
15. The system of claim 14, wherein the brake assembly comprises: a
first plate coupled to the secondary bearing actuator assembly, the
first plate having at least a first surface and a second surface,
the first surface having a plurality of teeth formed thereon; a
second plate having at least a first surface and a second surface,
the second plate second surface located substantially opposed to
the first plate first surface and having a plurality of teeth
formed thereon; and a brake actuator coupled to the second plate,
the brake actuator coupled to receive the brake control signals and
operable, in response thereto, to selectively move the second plate
second surface into and out of engagement with the first plate
first surface.
16. The system of claim 12, wherein the secondary bearing control
circuit is further adapted to receive a signal representative of an
electrical system supply voltage and is further operable, in
response thereto, to selectively supply the actuator control
signals.
17. The system of claim 12, wherein each secondary bearing position
sensor comprises a proximity sensor.
18. The system of claim 12, wherein the secondary bearing position
sensors comprise: an engage position sensor configured to supply an
engage signal when the secondary bearing assemblies are at least in
the engaged position; and a disengage position sensor configured to
supply a disengage signal when the secondary bearing assemblies are
at least in the disengaged position.
19. The system of claim 18, further comprising: a sensor mount
structure disposed proximate at least one secondary bearing
actuator assembly, the sensor mount structure having a main body
that includes at least a first end and a second end, the sensor
mount structure first end having the engage position sensor mounted
therein and the sensor mount structure second end having the
disengage position sensor mounted therein; a position semaphore
having at least a first end and a second end, the position
semaphore first end coupled to the at least one secondary bearing
actuator assembly and moveable therewith and the position semaphore
second end disposed between the sensor mount structure first and
second ends, wherein the engage and disengage position sensors are
each proximity sensors operable to supply position signals based on
proximity thereto of the position semaphore.
20. The system of claim 12, further comprising: one or more bearing
mount structures each coupled to one of the secondary bearing
assembly actuator assemblies, each bearing mount structure having
one or more of the secondary bearing assemblies mounted thereon,
wherein the secondary bearing actuator assemblies selectively move
the bearing mount structures to thereby move the secondary bearing
assemblies.
21. In an energy storage flywheel system having at least a flywheel
shaft and one or more primary bearing assemblies configured to
selectively rotationally support the flywheel shaft, a method of
selectively rotationally supporting the flywheel shaft via one or
more secondary bearing assemblies, comprising: determining whether
the primary bearing assemblies are operable to rotationally support
the flywheel shaft; upon determining that the primary bearing
assemblies are not operable to rotationally support the flywheel
shaft, moving at least one of the secondary bearing assemblies from
a disengaged position to an engaged position, to thereby
rotationally support the flywheel shaft via the secondary bearing
assemblies; and supplying a position signal representative of
secondary bearing assembly position at least when one of the
secondary bearing assemblies engages the shaft.
22. The method of claim 21, further comprising: selectively
inhibiting movement of the at least one secondary bearing assembly
in at least the engaged and disengaged positions.
23. The method of claim 21, wherein the energy storage flywheel
system is adapted to electrically couple to an electrical
distribution system, and wherein the method further comprises:
determining a voltage magnitude of the electrical distribution
system; and if the voltage magnitude is below a predetermined
value, moving at least one of the secondary bearing assemblies from
a disengaged position to an engaged position, to thereby
rotationally support the flywheel shaft via the secondary bearing
assemblies.
Description
TECHNICAL FIELD
[0001] The present invention relates to energy storage flywheel
systems and, more particularly, to a system and method of providing
back-up rotational support for an energy storage flywheel
system.
BACKGROUND
[0002] Many satellites and other spacecraft, as well as some
terrestrial stationary and vehicle applications, such as seagoing
vessels, can include one or more energy storage flywheel systems to
provide both a backup power source and to provide attitude control
for the vehicle. In such systems, each flywheel system is
controlled and regulated to balance the electrical demand in the
vehicle electrical distribution system, and may also be controlled
in response to programmed or remote attitude (or torque) commands
received by a main controller in the vehicle.
[0003] Many energy storage flywheel systems include one or more
components that are rotationally supported within a housing
assembly. These components, which may be referred to as the
rotating group, include, for example, an energy storage flywheel, a
motor/generator, and a shaft. In particular, the energy storage
flywheel and motor/generator may be mounted on the shaft, which may
in turn be rotationally supported in the housing assembly via one
or more bearing assemblies. In many instances, the shaft is
rotationally supported using one or more primary bearing
assemblies, and one or more secondary, or back-up, bearing
assemblies. For example, in many satellite and spacecraft
applications, the flywheel system may include one or more magnetic
bearing assemblies that function as the primary bearing assemblies,
and one or more mechanical bearing assemblies that function as the
secondary bearing assemblies. Typically, the primary bearing
assemblies are used to rotationally support the rotating group,
while the secondary bearing assemblies are otherwise disengaged
from the rotating group. If one or more of the primary bearing
assemblies is deactivated due, for example, to a malfunction, or
otherwise becomes inoperable to rotationally support the rotating
group, the secondary bearing assemblies will then engage, and
thereby rotationally support, the rotating group.
[0004] In some systems, the secondary bearing assemblies are
fixedly mounted and, upon deactivation of the primary bearing
assemblies, the shaft is brought into contact with the secondary
bearing assemblies. While safe and generally effective, this
configuration can cause damage to either or both the shaft and
secondary bearing assemblies if the shaft is rotating at a
relatively high speed when the primary bearing assemblies are
deactivated.
[0005] In other systems, the secondary bearing assemblies are
spring loaded, or otherwise biased, toward either the engaged or
disengaged position. If the secondary bearing assemblies are spring
loaded toward the disengaged position, then in order to move the
secondary bearing assemblies to the engaged position, an actuator
may be energized to overcome the spring load and move the bearing
assemblies to the engaged position. Conversely, if the secondary
bearing assemblies are spring loaded toward the engaged position,
then in order to move the secondary bearing assemblies to the
disengaged position, an actuator may be energized to overcome the
spring load and move the bearing assemblies to the disengaged
position. In either of these instances, the actuator may be
configured to rapidly move the secondary bearing assemblies into
contact with the shaft. This configuration, too, can cause damage
to the shaft and/or secondary bearing assemblies if the shaft is
rotating at a relatively high speed when the primary bearing
assemblies are deactivated.
[0006] Hence, there is a need for an auxiliary, or secondary,
bearing assembly system that improves on one or more of the
above-noted drawbacks. Namely, a bearing assembly system that
substantially eliminates, or at least lessens the likelihood of,
damage occurring to the shaft and/or secondary bearing assemblies
when the secondary bearing assemblies are engaged while the shaft
is rotating at relatively high speeds. The present invention
addresses one or more of these needs.
BRIEF SUMMARY
[0007] The present invention provides an auxiliary bearing system
and method that substantially eliminates damage to the shaft and/or
secondary bearing assemblies when the secondary bearing assemblies
are engaged while the shaft is rotating at relatively high
speeds.
[0008] In one embodiment, and by way of example only, an energy
storage flywheel system includes a shaft, a flywheel assembly, one
or more primary bearing assemblies, one or more secondary bearing
assemblies, one or more secondary bearing position sensors, a
secondary bearing control circuit, and one or more secondary
bearing actuators. The flywheel assembly is mounted on the shaft.
The primary and secondary bearing assemblies are each configured to
selectively rotationally support the shaft. The secondary position
sensors are each configured to supply position signals
representative of a position of one or more of the secondary
bearing assemblies. The secondary bearing control circuit is
adapted to receive one or more signals representative of primary
bearing assembly operability and the secondary bearing assembly
position signals and is operable, in response thereto, to
selectively supply actuator control signals. The secondary bearing
actuator assemblies are each coupled to one or more of the
secondary bearing assemblies. The actuator assemblies are each
further coupled to receive the actuator control signals from the
control circuit and are operable, in response thereto, to move the
secondary bearing assemblies to one of an engage position, in which
each secondary bearing assembly rotationally supports the shaft,
and a disengage position, in which each secondary bearing assembly
does not rotationally supports the shaft.
[0009] In another exemplary embodiment, an auxiliary bearing
control system for a system having a shaft and one or more primary
bearing assemblies includes one or more secondary bearing position
sensors, a secondary bearing control circuit, and one or more
secondary bearing assemblies. Each position sensor is configured to
supply position signals representative of a position of one or more
of the secondary bearing assemblies. The secondary bearing control
circuit is adapted to receive one or more signals representative of
primary bearing assembly operability and the secondary bearing
assembly position signals and is operable, in response thereto, to
selectively supply actuator control signals. Each secondary bearing
actuator assembly is coupled to one or more of the secondary
bearing assemblies, and is further coupled to receive the actuator
control signals from the control circuit and is operable, in
response thereto, to move the secondary bearing assemblies to one
of an engage position, in which each secondary bearing assembly
rotationally supports the shaft, and a disengage position, in which
each secondary bearing assembly does not rotationally supports the
shaft.
[0010] In yet another exemplary embodiment, a method of selectively
rotationally supporting a flywheel shaft via one or more secondary
bearing assemblies in an energy storage flywheel system having at
least a flywheel shaft and one or more primary bearing assemblies
configured to selectively rotationally support the flywheel shaft
includes determining whether the primary bearing assemblies are
operable to rotationally support the flywheel shaft. Upon
determining that the primary bearing assemblies are not operable to
rotationally support the flywheel shaft, at least one of the
secondary bearing assemblies is moved from a disengaged position to
an engaged position, to thereby rotationally support the flywheel
shaft via the secondary bearing assemblies. A position signal
representative of secondary bearing assembly position is supplied
at least when one of the secondary bearing assemblies engages the
shaft.
[0011] Other independent features and advantages of the preferred
auxiliary bearing system and method will become apparent from the
following detailed description, taken in conjunction with the
accompanying drawings which illustrate, by way of example, the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a simplified schematic representation of an
exemplary energy storage flywheel system that includes an exemplary
embodiment of a retention system in a disengaged configuration;
and
[0013] FIG. 2 is a simplified schematic representation of the
system shown in FIG. 1, but with the exemplary retention system in
an engaged configuration;
[0014] FIG. 3 is a functional block diagram of an exemplary
embodiment of one energy storage flywheel system that may be used
in the system of FIG. 1;
[0015] FIGS. 4 and 5 are perspective and cross section views,
respectively, of a physical embodiment of the energy storage
flywheel system of FIG. 3;
[0016] FIGS. 6 and 7 are close-up, partial cross section views of
the energy storage flywheel system of FIGS. 4 and 5;
[0017] FIG. 8 is a perspective view of a portion of an auxiliary
bearing actuator assembly that may be used in the system of FIGS.
3-7; and
[0018] FIG. 9 is a functional block diagram of an exemplary
auxiliary bearing system that may be used in the system of FIGS.
3-7.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0019] Before proceeding with a detailed description, it is to be
appreciated that the described embodiment is not limited to use in
conjunction with a spacecraft. Thus, although the present
embodiment is, for convenience of explanation, depicted and
described as being implemented in a satellite, it will be
appreciated that it can be implemented in other systems and
environments, both terrestrial and extraterrestrial.
[0020] Turning now to the description and with reference first to
FIG. 1, a functional block diagram of an exemplary power and
attitude control system 100 for a spacecraft is shown. The system
100 includes a main controller 102, a primary power source 104, and
a plurality of flywheel systems 106 (106-1, 106-2, 106-3, . . .
106-N). A perspective view of an exemplary physical embodiment of a
spacecraft 200 that may use the system 100 is illustrated in FIG.
2.
[0021] The main controller 102 receives attitude commands (or
torque commands) from, for example, an earthbound station or its
onboard autopilot 108, and monitors the electrical distribution
system 114, and appropriately controls the operation of the
flywheel systems 106. In response to the torque commands, the
flywheel systems 106 are controlled to induce appropriate attitude
disturbances in the spacecraft, and thereby control spacecraft
attitude. In addition, depending upon the state of the electrical
distribution system 114, the flywheel systems 106 are controlled to
either supply electrical energy to, or draw electrical energy from,
the electrical distribution system. One or more spacecraft dynamic
sensors, such as one or more attitude sensors 110 and one or more
rate sensors 112, sense spacecraft attitude and attitude
rate-of-change, respectively, and supply feedback signals
representative thereof to the main controller 102. A more detailed
description of the main controller 102 and the process it
implements to control power and attitude is provided further
below.
[0022] The primary power source 104, as its name connotes, is the
primary source of electrical power to the electrical distribution
system 114. In the depicted embodiment, in which the system 100 is
implemented in a spacecraft, the primary power source 104 is one or
more solar panels, each of which includes an array of solar cells
to convert light energy into electrical energy. The solar panels
104 may be attached to the satellite itself or to fixed or moveable
structures that extend from the satellite. When the spacecraft 200
is positioned such that it does not receive sunlight, such as, for
example, when it is in the Earth's shadow, a backup electrical
power source is needed. As was alluded to above, in addition to
providing attitude control, the flywheel systems 106 also function
as a backup power source. The flywheel systems 106 may also provide
electrical power if the power demanded by the electrical loads
exceeds the capacity of the primary power source 104. It will be
appreciated that another backup power source, such as a battery 115
(shown in phantom in FIG. 1), may also be provided.
[0023] The system 100 includes N number of energy storage flywheel
systems 106 (106-1, 106-2, 106-3, . . . 1-6-N). The system 100 is
preferably configured so that some of the flywheel systems 106 are
active, while one or more of the remaining flywheel systems 106 is
in a standby, inactivated state. Thus, the system 100 is at least
single fault tolerant. The number of flywheel systems 106 that are
active may vary, depending on system requirements. As will be
discussed more fully below, in a particular preferred embodiment,
four flywheel systems 106 are active and the remaining are
inactive.
[0024] The flywheel systems 106 each include a flywheel control
module 116 (116-1, 116-2, 116-3, . . . 116-N) and flywheel hardware
118 (118-1, 118-2, 118-3, . . . 118-N). The flywheel control
modules 116 are each in operable communication with the main
controller 102 and, in the depicted embodiment, are in
communication with one another via a data bus 111. The main
controller 102, as was noted above, supplies attitude control
commands to the each of the flywheel control modules 116. In turn,
the flywheel control modules 116 control the relative attitudes and
angular velocities of the associated flywheel hardware 118 to
effect attitude control of the spacecraft 200. The flywheel control
modules 116 also respond to commands from the main controller 102
to control the operation of the associated flywheel hardware 118 in
either a motor mode or a generator mode, and the rotational
acceleration of the associated flywheel hardware 118 in each mode.
The flywheel control modules 116, as is discussed in more detail
below, also monitor various parameters of the associated flywheel
hardware 118, and supply representative signals to the main
controller 102. A block diagram of an exemplary embodiment of one
flywheel system 106 is illustrated in FIG. 3, and will now be
discussed in detail.
[0025] In the depicted embodiment, the flywheel control modules 116
each include four separate controllers, a gimbal controller 302, a
motor/generator controller 304, a magnetic bearing controller 306,
and an auxiliary bearing controller 308. The flywheel hardware 118
each include an energy storage flywheel assembly 310, gimbal
hardware 320, motor/generator hardware 330, magnetic bearing
hardware 340, and auxiliary bearing hardware 350. The gimbal
controller 302 receives gimbal angle velocity commands from the
main controller 102, and supplies appropriate control signals to,
and receives various feedback signals from, the gimbal hardware
320, to effect attitude control. At least some of the feedback
signals the gimbal controller 320 receives are representative of
the gimbal hardware 320 response to the supplied control signals.
The gimbal controller 302 also supplies these feedback signals to
the main controller 102.
[0026] In the depicted embodiment, the gimbal hardware 320 is a
gimbal frame that includes one or more gimbal assemblies 322, one
or more gimbal actuators 324, and one or more gimbal sensors 326.
The flywheel assembly 310 is rotationally mounted in the gimbal
frame 320, about a gimbal axis, via the gimbal assemblies 322. The
gimbal axis is perpendicular to the spin axis of the energy storage
flywheel assembly 310. The gimbal actuator 324 is coupled to the
gimbal frame 320, and is also coupled to receive the control
signals from the gimbal controller 302. As is generally known,
attitude control in a spacecraft may be implemented by changing the
gimbal angles at certain rates (e.g., angular velocities). Thus, in
response to the commands received from the main controller 102, the
gimbal controller 302 supplies appropriate control signals to the
gimbal actuators 324. In response to these control signals, the
gimbal actuators appropriately position the flywheel assembly 310
with respect to the gimbal frame 320 at the appropriate angular
velocities. The gimbal sensors 326 include sensors that can sense
at least the position and rate of the flywheel with respect to the
gimbal frame 320, and supply position and rate feedback signals to
the gimbal controller 302 and to the main controller 102.
[0027] The motor/generator controller 304 receives a signal
representative of the bus voltage of the electrical distribution
system 114 and, in response, configures the motor/generator
hardware 330 to operate as either a motor or a generator. The
motor/generator controller 304 also receives commands from the main
controller 102 and, in response, controls the rotational
acceleration of the motor/generator and thus the flywheel assembly
310. To do so, the motor/generator controller 304 is configured to
selectively implement either a motor control law 311 or a generator
control law 313. The motor/generator controller 304 also receives
various feedback signals from the motor/generator hardware 330. At
least some of the feedback signals received by the motor/generator
controller 304 are representative of the motor/generator hardware
330 response to the supplied control signals. The motor/generator
controller 304 supplies one or more of the feedback signals it
receives from the motor/generator hardware 330 to the main
controller 102.
[0028] The motor/generator hardware 330 includes a motor/generator
332 and one or more sensors 334. The motor/generator 332 may be any
one of numerous motor/generator sets known now, or in the future,
and includes a main rotor that is coupled to the rotor of the
flywheel assembly 310. The sensors 334 include one or more
temperature sensors and one or more commutation sensors. When the
bus voltage of the electrical distribution system 114 is
sufficiently high, the motor/generator controller 304 implements
the motor control law 311 and the motor/generator 332 is operated
as a motor. During operation as a motor, the motor/generator 332
spins up the flywheel assembly 310, to store rotational kinetic
energy. Conversely, when the bus voltage of the electrical
distribution system 114 drops to some predetermined magnitude, the
motor/generator controller 304 implements the generator control law
313 and the motor/generator 332 is operated as a generator. During
its operation as a generator, the motor/generator 332 spins down
the flywheel assembly 310, converting the flywheel's stored
rotational kinetic energy to electrical energy. As was previously
discussed, changes in the rotational speed of the flywheel assembly
310 can impact the attitude of the spacecraft. Thus, in both the
motor mode and generator mode, the flywheel assembly 310 is spun
up, or spun down, to a rotational velocity at an acceleration
commanded by the main controller 102.
[0029] The magnetic bearing controller 306 may also receive one or
more commands from the main controller 102. The magnetic bearing
controller 306, in accordance with a control law, supplies
appropriate command signals to, and receives various feedback
signals from, the magnetic bearing hardware 340. At least some of
the feedback signals received by the magnetic bearing controller
306 are representative of the magnetic bearing hardware 340
response to the supplied control signals. As will be described in
more detail further below, the magnetic bearing controller 306, at
least in the depicted embodiment, supplies one or more of the
feedback signals it receives to the auxiliary bearing controller
308. Moreover, similar to the gimbal controller 302, the magnetic
bearing controller 306 may additionally supply one or more of the
feedback signals it receives to the main controller 102.
[0030] The magnetic bearing hardware 340 functions to rotationally
support or levitate, in non-contact fashion, the energy storage
flywheel assembly 310, and is the primary bearing system for the
energy storage flywheel assembly 310. In the depicted embodiment,
the magnetic bearing hardware 340 implements active magnetic
bearings, and includes electromagnetic actuators 342 and one or
more sensors 344 such as, for example, position sensors,
temperature sensors, and speed sensors. The position sensors 344
sense the position of the flywheel rotor (not illustrated) and
supply appropriate position signals to the magnetic bearing
controller 306. The magnetic bearing controller 306, in accordance
with the control law, supplies the appropriate current magnitude to
the electromagnetic actuators 342, which in turn generate magnetic
forces of the appropriate magnitude to appropriately position the
flywheel rotor. Although active magnetic bearings are described as
being implemented in the system shown in FIG. 3, it will be
appreciated that the magnetic bearing hardware 340 could be
configured to implement passive magnetic bearings. Alternatively,
other types of bearing assemblies could be used to implement the
primary bearing assemblies such as, for example, non-magnetic
rolling element bearings.
[0031] The auxiliary bearing controller 308 receives various
signals representative of magnetic bearing hardware operability and
various feedback signals from the auxiliary bearing hardware 350.
In response to these signals, the auxiliary bearing controller 308
supplies appropriate command signals to the auxiliary bearing
hardware 350. In particular, as will be described in more detail
further below, the auxiliary bearing controller 308 receives a
feedback signal representative of the position of the auxiliary
bearing hardware. As will also be described further below, the
auxiliary bearing controller 308 may additionally receive a signal
representative of the bus voltage of the electrical distribution
system 114 and, in response, supply appropriate command signals to
the auxiliary bearing hardware 350.
[0032] The auxiliary bearing hardware 350 is used to rotationally
support the energy storage flywheel assembly 310 when the magnetic
bearing hardware 340 is inoperable, or is otherwise not capable of
properly doing so. The auxiliary bearing hardware 350, a preferred
embodiment of which will be described in more detail further below,
includes an actuator assembly 352, one or more auxiliary (or
secondary) bearing assemblies 354, one or more position sensors
356, and a brake assembly 358. The actuator assembly 352, in
response to appropriate command signals from the auxiliary bearing
controller 308, moves the auxiliary bearing assemblies 354 to
either an engage position or a disengage position. In the disengage
position, which is the normal position of the auxiliary bearing
assemblies 354, the auxiliary bearing assemblies 354 are disengaged
from, and do not rotationally support, the flywheel assembly 310.
Rather, the flywheel assembly 310 is rotationally supported by the
magnetic bearing hardware 340. Conversely, in the engage position
the auxiliary bearing assemblies 354 engage, and rotationally
support, the flywheel assembly 310. A more detailed description of
a particular preferred embodiment of the auxiliary bearing hardware
350 and the operation of the components that make up the auxiliary
bearing hardware 350 will be described in more detail further
below.
[0033] With reference first to FIGS. 4 and 5, which depict an
exemplary physical embodiment of an energy storage flywheel system
106, it is seen that the exemplary flywheel system 106 includes a
housing assembly 402, which is rotationally mounted in the gimbal
frame 322 via two gimbal bearings 404 (only one shown). A single
gimbal actuator 324 is mounted on the gimbal frame 322 and, as was
noted above, receives control signals from the gimbal controller
302 (not shown in FIGS. 4 and 5) to position the housing assembly
402 at the appropriate angular velocities, to thereby effect
attitude control.
[0034] The housing assembly 402 includes a central section 406, two
end sections 408 and 410, a motor/generator housing 412, an
auxiliary bearing housing 414, and an auxiliary motor housing 416.
Although the housing assembly 402 is depicted as being constructed
of numerous sections that are coupled together, it will be
appreciated that it could be formed as an integral structure. In
any event, the motor/generator housing 412 is coupled to the
housing assembly second end section 410, the auxiliary bearing
housing 414 is coupled to the housing assembly first end section
408, and the the auxiliary motor housing 416 is coupled to the
auxiliary bearing housing 414.
[0035] The motor/generator 332 stator is mounted in the
motor/generator housing 412 and the motor/generator 332 rotor is
coupled to the flywheel assembly 310. The flywheel assembly 310, as
shown more particularly in FIG. 5, includes a shaft assembly 502, a
hub 504, and a flywheel rim 506. The shaft assembly 502 is
rotationally mounted in the housing assembly 402 via either two
sets of the magnetic bearing hardware 340 or, as will be described
in more detail further below, two auxiliary bearing assemblies
354a, 354b. The hub 504 is preferably constructed of a
high-strength metal alloy, and is mounted on the shaft assembly
502. The hub 504 may be constructed in any one of numerous
configurations including, for example, a solid configuration, a
spoke-type configuration, or a combination thereof. The flywheel
rim 506 is mounted on, and surrounds, the hub 504, and is
preferably constructed of a material having a high
strength-to-density ratio such as, for example, filament wound
carbon fiber.
[0036] Turning now to FIGS. 6 and 7, close-up views of the
auxiliary bearing hardware 350 are shown, and will now be described
in more detail. One of the auxiliary bearing assemblies 354a is
housed in the auxiliary bearing housing 414, and the other
auxiliary bearing assembly 354b is housed within the
motor/generator housing 412. The auxiliary bearing assemblies 354a,
354b may be any one of numerous types of non-magnetic bearing
assemblies. In the depicted embodiment, however, each is a rolling
element bearing assembly, and are mounted on a touchdown cup 602
and 702, respectively. The auxiliary bearing assembly 354a and
touchdown cup 602 that are mounted in the auxiliary bearing housing
414 are coupled to the actuator assembly 352. As will be described
more fully below, the actuator assembly 352, in response to
commands from the auxiliary bearing assembly controller 308,
selectively moves the touchdown cup 602 in and out of contact with
the flywheel shaft assembly 502, to thereby engage and disengage,
respectively, the auxiliary bearing assemblies 354a, 354b.
[0037] The auxiliary bearing actuator assembly 352 may be any one
of numerous types of actuator assemblies, but in the depicted
embodiment it is a ballscrew actuator 604 that is driven by a motor
606. As is generally known, a ballscrew actuator is configured such
that at least a portion of the actuator translates in response to
receipt of a rotational drive force. The motor 606 is housed in the
auxiliary motor housing 416 is coupled to the actuator 604 via a
motor output shaft 608 that extends into the auxiliary bearing
housing 414. The motor 606 may be any one of numerous types of
motors including, but not limited to, hydraulic, pneumatic, and
electric. Preferably, however, the motor 606 is electric and,
although it could be any one or numerous types of AC or DC motors,
it is preferably a DC torque motor. As will be described more fully
below, the motor 606 is coupled to receive actuator control signals
from the auxiliary bearing control circuit 308 and, in response to
the control signals, supplies an appropriate drive force to the
actuator 604, which in turn appropriately engages or disengages the
auxiliary bearing assemblies 354a, 354b.
[0038] The brake assembly 358 is mounted within the auxiliary motor
housing 416, and is also coupled to the motor output shaft 608. As
will also be described more fully below, the brake assembly 358 is
coupled to receive brake control signals supplied from the
auxiliary bearing control circuit 308 and, in response, selectively
prevents or allows rotation of the motor output shaft 608, and thus
selectively prevents or allows movement of the actuator 604 and
auxiliary bearing assembly 354a. It will be appreciated that the
brake assembly 358 may be implemented using any one of numerous
brake types and configurations. In a particular preferred
embodiment the brake assembly 358 is a tooth brake assembly that is
configured to be engaged when not energized, and is energized to
release. This particular preferred embodiment is shown coupled to
the actuator assembly 352 in FIG. 8, and will now be described in
more detail. It will be appreciated, however, that for clarity of
illustration, the actuator assembly 352 is depicted in FIG. 8
without the motor 604 and associated housings.
[0039] As FIG. 8 shows, the brake assembly 358 includes a first
brake plate 610, a second brake plate 612, and a brake solenoid
614. The first brake plate 610 surrounds, and rotates with, a
portion of the motor output shaft 608, and includes an engagement
surface 616, and a non-engagement surface 618. The engagement
surface 616 includes a plurality of engagement teeth 620, which may
be either formed into the first plate engagement surface 616 or
separately coupled thereto. With reference to both FIGS. 6 and 8,
it is seen that the first brake plate 610 and the section of the
motor output shaft 608 that the first brake plate surrounds are
configured such that the first brake plate 610 may translate along
a portion of the motor output shaft 608. It is noted that the
second brake plate 612 is biased toward the first brake plate 610
by a non-illustrated spring, so that when the brake assembly 352 is
not energized it will default to the engaged position.
[0040] The second brake plate 612 is fixedly mounted in the
auxiliary motor housing 416. Similar to the first brake plate 610,
the second brake plate 612 includes an engagement surface 622 and a
non-engagement surface 624. The second brake plate engagement
surface 622 includes a plurality of engagement teeth 626, which may
also be formed into the second plate engagement surface 622 or
separately coupled thereto. It will be appreciated that the
engagement teeth 620 and 626 on the first and second plate
engagement surfaces 616 and 622, respectively, are preferably
configured to mesh with one another when the first 610 and second
612 brake plates engage one another.
[0041] The brake solenoid 614 is coupled to the second brake plate
612 and, in response to the brake actuator signals supplied from
the auxiliary bearing controller 308, selectively moves the second
brake plate 612 into and out of engagement with the first brake
plate 610, thereby disengaging the brake assembly 358. With the
brake assembly 358 disengaged, the motor output shaft 608 is free
to rotate. Conversely, when the brake solenoid 614 is de-energized,
the non-illustrated spring supplies a bias force that moves the
second brake plate 612 into engagement with the first brake plate
610, thereby engaging the brake assembly 358. As was noted above,
when the brake plates 610, 612 engage one another, the respective
engagement teeth 620, 626 mesh with one another. In this position,
because the second brake plate 612 does not rotate, the first brake
plate 610 is prevented from rotating. Since the first brake plate
610 is coupled to the motor output shaft 608, which is in turn
coupled to the actuator 604, actuator movement is prevented.
[0042] With continued reference to FIG. 8, a particular preferred
configuration and implementation of the auxiliary bearing position
sensors 356 will now be described. In the depicted embodiment, two
position sensors, an engaged position sensor 356a and a disengaged
position sensor 356b, are used. Although the position sensors 356
may be any one of numerous types of known position sensors, in the
depicted embodiment, the position sensors 356 are proximity
sensors. The position sensors 356 are each mounted in a sensor
mount structure 802. The sensor mount structure 802 is
substantially C-shaped, includes a first end 804 and a second end
806, and is coupled to the auxiliary bearing actuator 604. The
engaged position sensor 356a is mounted to the mount structure
first end 802 and the disengaged position sensor 356b is mounted to
the mount structure second end 804. As FIG. 8 also shows, a
position semaphore 808 is coupled to the motor output shaft 608 and
extends between mount structure first 804 and second 806 ends. The
position semaphore 808 rotates with the motor output shaft 608. As
the position semaphore 808 rotates, it is positioned proximate
either the engaged 356a or disengaged 356b position sensor, to
indicate that the auxiliary bearing assemblies 354 are engaged or
disengaged, respectively. As was noted above, the position sensors
356a, 356b supply signals representative of the position of the
auxiliary bearings 354 to the auxiliary bearing controller 308.
[0043] The auxiliary bearing system, the components that make up
the auxiliary bearing system, and implementation of the auxiliary
bearing system into a physical environment, such as an energy
storage flywheel system 106, have been described. With reference
now to FIG. 9, which depicts a particular preferred embodiment of
the auxiliary bearing system 900 apart from the remaining
components, systems, and subsystems that make up an energy storage
flywheel system 106, the operation of the auxiliary bearing system
900 will now be described.
[0044] The auxiliary bearing controller 308, as was noted above,
receives a signal representative of electrical distribution system
bus voltage 902, and signals representative of magnetic bearing
hardware operability. In the depicted embodiment, these latter
signals include a signal representative of magnetic bearing current
904 and a signal representative of magnetic bearing position fault
906. It will be appreciated that these are merely exemplary of the
types of signals that may be used to indicate magnetic bearing
hardware operability. It will additionally be appreciated that
these signals may be supplied from various signal sources within
the flywheel system 106. In the depicted embodiment, however, these
signals, as shown in FIG. 3, are supplied from the magnetic bearing
controller 306. The auxiliary bearing controller 308 is also
configured to receive position signals from each of the auxiliary
bearing positions sensors 354a, 354b. In the depicted embodiment,
the auxiliary bearing controller 308 supplies appropriate power
and/or excitation to the position sensors 354a, 354b, though it
will be appreciated that this could come from other sources.
[0045] In most circumstances, the flywheel system 106 into which
the auxiliary bearing system 900 is installed uses the magnetic
bearings to 340 to rotationally support the flywheel shaft assembly
502. However, if one or more of the signals 902-906 supplied to the
auxiliary bearing controller indicate that one or more of the
magnetic bearings is inoperable, misaligned, or otherwise incapable
of rotationally supporting the flywheel shaft assembly 502, the
auxiliary bearing controller 308 will then command the auxiliary
bearing assemblies 354a, 354b to engage the flywheel shaft assembly
502. To do so, the auxiliary bearing controller 308 supplies an
appropriate brake release command signal to the brake assembly 358,
to thereby release the brake assembly 358 and allow movement of the
auxiliary bearing actuator assembly 352. As was described above, in
a particular preferred embodiment, the brake release command signal
is merely an appropriate power signal that energizes the brake
solenoid 614, which causes the first 610 and second 612 brake
plates to disengage one another.
[0046] Upon release of the brake assembly 358, or substantially
simultaneous with supplying the brake release command, the
auxiliary bearing controller 308 additionally supplies an
appropriate command signal to the auxiliary bearing actuator
assembly 352. For the particular preferred embodiment described
above, the auxiliary bearing controller 308 supplies a signal of
appropriate polarity to the DC torque motor 606 to cause it to
rotate, and thus supply a drive force, in the engage direction. In
response to the drive force supplied from the torque motor 606, the
actuator 604 translates, which in turn translates the touchdown cup
602 into contact with the flywheel shaft assembly 502, which in
turn causes the flywheel shaft assembly to engage the other
touchdown cup 702. Since the auxiliary bearing assemblies 354a and
354b are mounted on the touchdown cups 602 and 702, respectively,
the flywheel shaft assembly 502 will then be rotationally supported
by the auxiliary bearing assemblies 354a, 354b.
[0047] As the torque motor 606 begins rotating in the engage
direction, the position semaphore 808 (not shown in FIG. 8), which
is coupled to the motor output shaft 608, is rotated away from the
disengaged position sensor 356b, and toward the engaged position
sensor 356a. As was noted above, the position sensors 356a, 356b
and position semaphore 608 are configured such that the position
semaphore 608 is disposed proximate the engaged position sensor
356a when the auxiliary bearing assemblies 354a, 354b engage, and
thus rotationally support, the flywheel shaft assembly 502. Thus,
when the auxiliary bearing actuator assembly 352 moves the
auxiliary bearing assemblies 354a, 354b into the engaged position,
the engaged position sensor 356a supplies an appropriate position
signal to the auxiliary bearing controller 308.
[0048] Upon receipt of the appropriate position signal from the
engaged position sensor 356a indicating that the auxiliary bearing
assemblies 354a, 354b are in the engaged position, the auxiliary
bearing assembly controller 308 will de-energize both the torque
motor 606 and brake assembly 358. As a result, the torque motor 606
stops rotating, and the brake assembly 358 engages. It will be
appreciated that auxiliary bearing controller 308 could be
configured to de-energize the torque motor 606 and brake assembly
358 either simultaneously, or sequentially. The auxiliary bearing
assemblies 354a, 354b will thus be locked in the engaged position
until the auxiliary bearing controller issues a disengage
command.
[0049] When the auxiliary bearing assemblies 354a, 354b are no
longer needed to rotationally support the flywheel 310, the
auxiliary bearing controller 308 issues the appropriate command
signals to disengage the auxiliary bearing assemblies 354a, 354b.
In particular, the auxiliary bearing controller 308 supplies a
brake release command signal to the brake assembly 358 and a
disengage command to the actuator assembly 352. Upon receipt of the
brake release command, the brake assembly 358, as was described
above, releases and allows movement of the auxiliary bearing
actuator assembly 352.
[0050] The auxiliary bearing controller 308 additionally supplies a
signal of appropriate polarity to the DC torque motor 606 to cause
it to rotate, and thus supply a drive force, in the disengage
direction. This signal may be supplied upon release of the brake
assembly 358, or substantially simultaneous with supplying the
brake release command. In any case, the actuator 604, in response
to the drive force supplied from the torque motor 606, translates
the touchdown cup 602 out of contact with the flywheel shaft
assembly 502, which in turn causes the flywheel shaft assembly to
disengage the other touchdown cup 702. Thus, the flywheel shaft
assembly 502 will no longer be rotationally supported by the
auxiliary bearing assemblies 354a, 354b.
[0051] The energy storage flywheel system and method described
herein includes an auxiliary bearing control system 900 that
rotationally supports the flywheel system rotating group when the
primary means of rotational support is not available or is
otherwise non-operable. The system 900 substantially eliminates, or
at least lessens the likelihood of, damage occurring to the
rotating group and/or auxiliary bearing assemblies when the
auxiliary bearing assemblies are engaged while the rotating group
is rotating at relatively high speeds.
[0052] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt to a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
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